Liquid transport method and liquid transport apparatus

ABSTRACT

A liquid transport method includes rotating a cam from a reference position of rotation of the cam rotating for transporting liquid; determining whether or not the cam rotates to a predetermined rotational angle on the basis of an image of a liquid transport apparatus captured when the cam is rotated and stopped; and memorizing a signal value indicating a rotational angle of the cam from the reference position of rotation until the cam rotates to the predetermined rotational angle. With this method, the relationship between a signal original point and a pump original point is obtained easily.

BACKGROUND

1. Technical Field

The present invention relates to a liquid transport method and a liquidtransport apparatus.

2. Related Art

A micro pump disclosed in JP-A-2013-24185 is known as a liquid transportapparatus configured to transport liquid. The micro pump includes aplurality of fingers arranged along a tube, and a cam presses thefingers in sequence, so that the tube is collapsed and hence liquid istransported. An encoder for measuring a rotational angle of the cam isprovided.

In a liquid transport using the cam and the fingers, liquid feedingproperties include periodicity. Although a signal output from theencoder has periodicity, a position of a reference point of an outputsignal (hereinafter, referred to as “signal original point”) in onecycle differs from one machine to another. Therefore, it is required toobtain a relationship between the signal original point and a rotationalangle as a reference of the cam (hereinafter, referred to as “pumporiginal point”) in advance in order to control the liquid transport.

In terms of this point, the relationship between the signal originalpoint and the pump original point may be obtained by detecting an amountof transportation by actually transporting the liquid. However, sincethe amount of transportation is small, detection of the amount oftransportation requires high degree of accuracy, so that this method isnot suitable for mass production.

SUMMARY

An advantage of some aspects of the invention is to obtain arelationship between a signal original point and a pump original pointeasily.

An aspect of the invention provides a liquid transport method for aliquid transport apparatus, including: rotating a cam from a referenceposition of rotation of the cam rotating for transporting liquid;determining whether or not the cam rotates to a predetermined rotationalangle on the basis of an image of the liquid transport apparatuscaptured when the cam is rotated and stopped; and memorizing a signalvalue indicating a rotational angle of the cam from the referenceposition of rotation until the cam rotates to the predeterminedrotational angle.

Other characteristics of the aspects of the invention will be apparentfrom the specification and attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a general perspective view of a liquid transport apparatus ofa first embodiment.

FIG. 2 is an exploded view of the liquid transport apparatus of thefirst embodiment.

FIG. 3 is a cross-sectional view of the liquid transport apparatus ofthe first embodiment.

FIG. 4 is a perspective top view of an interior of the liquid transportapparatus of the first embodiment.

FIG. 5 is a schematic explanatory drawing of a pump unit of the firstembodiment.

FIG. 6 is a block diagram for explaining a measuring unit and a controlunit of the liquid transport apparatus.

FIG. 7 is an explanatory drawing of a cam-side reflecting portion formedon a cam gear.

FIG. 8 is an explanatory drawing of first and second reflecting portionsformed on a rotor.

FIG. 9 is a graph showing a relationship between an amount of rotationof a cam and an accumulated amount of transportation.

FIG. 10A is an explanatory drawing relating to a reverse flow of liquid.

FIG. 10B is an explanatory drawing relating to a reverse flow of liquid.

FIG. 11 is a partial enlarged drawing of the cam, the rotor, atransmitting wheel, a cam side measuring unit, and first and secondmeasuring units.

FIG. 12 is an explanatory drawing illustrating a relationship betweensignals CAM_Z, ROT_Z and ROT_A.

FIG. 13 is an explanatory drawing illustrating a relationship betweenthe signals CAM_Z, and ROT_A.

FIG. 14 is a flowchart illustrating a procedure for specifying a signaloriginal point.

FIG. 15 is a schematic diagram for explaining pump original pointdetermination.

FIG. 16 is a flowchart illustrating a procedure for the pump originalpoint determination.

FIG. 17 is a schematic drawing illustrating an example of a pump unit ofa second embodiment.

FIG. 18 is a schematic drawing illustrating an example of a pump unit ofa third embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

According to the specification and the attached drawings, at least thefollowings become apparent.

An aspect of the invention provides a liquid transport method for aliquid transport apparatus including: rotating a cam from a referenceposition of rotation of the cam rotating for transporting liquid;determining whether or not the cam rotates to a predetermined rotationalangle on the basis of an image of the liquid transport apparatuscaptured when the cam is rotated and stopped; and memorizing a signalvalue indicating a rotational angle of the cam from the referenceposition of rotation until the cam rotates to the predeterminedrotational angle.

A liquid transport method using a tube; a cam; a finger arranged betweenthe tube and the cam; a drive unit configured to rotate the cam; anencoder configured to output a rotational angle of the cam; and an imagepickup unit configured to capture an image of the cam, and includesobtaining a reference point of a signal output from the encoder;rotating the cam from the reference point of the signal; determiningthat the cam reaches a predetermined rotational angle on the basis of animage captured by the image pickup unit when the cam is rotated andstopped; and memorizing a counted value of an output signal of theencoder until the cam reaches the predetermined rotational angle fromthe reference point of the signal.

With the liquid transport method as described above, the relationshipbetween the signal original point and the pump original point may beobtained easily.

A position detection mark provided on the cam may be detected from theimage to detect the rotational angle of the cam. By providing theposition detection mark on the cam, the rotational angle of the cam canbe detected easily from the captured image, so that the relationshipbetween the signal original point and the pump original point can beobtained easily.

The rotational angle of the cam may be detected by detecting an edge ofthe position detection mark to detect the rotational angle of the cam.Since the position detection mark and the rotational angle of the camcorrespond to each other, whether the cam reaches the rotational anglecorresponding to the pump original point can be obtained easily bydetecting the edge of the mark.

A position of a pressing member configured to press a member whichdefines a flow channel of the liquid may be detected in association withthe rotation of the cam from the image to detect the rotational angle ofthe cam.

A position of the finger may be detected from the image to detect therotational angle of the cam. Since the positions of the fingerscorrespond to the rotational angle of the cam, the rotational angle ofthe cam is detected by detecting the positions of the fingers, and hencethe relationship between the signal original point and the pump originalpoint may be obtained easily.

The rotational angle of the cam when the reversely flowed liquid returnsby an amount corresponding to the reverse flow may be used as areference of the predetermined angle. Accordingly, control of a constantamount transportation of liquid is facilitated.

A liquid transport apparatus includes: a cam configured to rotate fortransporting liquid, and a control unit configured to read a memorizedsignal value indicating a rotational angle of the cam rotating from areference position of rotation to a predetermined rotational angle,determine whether or not the cam rotates from the reference position tothe predetermined rotational angle, and rotate the cam to a desiredrotational angle with reference to a position where the cam isdetermined to have rotated to the predetermined rotational angle.

With the liquid transport apparatus as described above, the relationshipbetween the signal original point and the pump original point may beobtained easily.

A rotational position measuring apparatus configured to measure arotational position of a cam in a liquid transport apparatus includingthe cam configured to rotate to transport liquid, and an encoderconfigured to output a rotational angle of the cam, includes: a camrotating unit configured to rotate the cam from a reference position ofrotation of the cam; a determining unit configured to determine whetheror not the cam rotates to a predetermined rotational angle on the basisof an image of the liquid transport apparatus captured when the cam isrotated and stopped; and a setting unit configured to memorize a countedvalue of the encoder during the rotation of the cam from the referenceposition of rotation to the predetermined rotational angle in the liquidtransport apparatus.

A rotational position measuring apparatus provided with a liquidtransport apparatus having a tube; a cam; a finger arranged between thetube and the cam; a drive unit configured to rotate the cam; and anencoder configured to output a rotational angle of the cam, and an imagepickup unit configured to capture an image of the liquid transportapparatus, and configured to measure a rotational position of the cam,includes a reference point searching unit configured to obtain areference point of a signal from the encoder; a cam rotating unitconfigured to rotate the cam from the reference point of the signal fromthe encoder; a determining unit configured to determine that the camreaches a predetermined rotational angle on the basis of an imagecaptured by the image pickup unit when the cam is rotated and stopped;and a memory unit configured to memorize a counted value of the encoderuntil the cam reaches the predetermined rotational angle from thereference point of the signal.

With the rotational position measuring apparatus as described above, therelationship between the signal original point and the pump originalpoint may be obtained easily.

First Embodiment Liquid Transport Apparatus General Configuration

FIG. 1 is a general perspective view of a liquid transport apparatus 1.FIG. 2 is an exploded view of the liquid transport apparatus 1. Asillustrated in these drawings, a side (biological body side) where theliquid transport apparatus 1 is adhered is referred to as “down” and anopposite side may be referred to as “up” in the description.

The liquid transport apparatus 1 is an apparatus configured to transportliquid. The liquid transport apparatus 1 includes a main body 10, acartridge 20, and a patch 30. The main body 10, the cartridge 20, andthe patch 30 are separable as illustrated in FIG. 2, and are assembledintegrally when in use as illustrated in FIG. 1. The liquid transportapparatus 1 is preferably used for infusing liquid stored in thecartridge 20 (for example, insulin) regularly, for example by adheringthe patch 30 to the biological body. In the case where the liquid storedin the cartridge 20 is finished up, the cartridge 20 is replaced.However, the main body 10 and the patch 30 are continuously used.

Pump Unit

FIG. 3 is a cross-sectional view of the liquid transport apparatus 1.FIG. 4 is a perspective top view of an interior of the liquid transportapparatus 1, and also illustrates a configuration of a pump unit 5. FIG.5 is a schematic explanatory drawing of the pump unit 5.

The pump unit 5 has a function as a pump for transporting liquid storedin the cartridge 20, and includes a tube 21, a plurality of fingers 22,a cam 11, and a drive mechanism 12.

The tube 21 is a tube for transporting liquid. An upstream side of thetube 21 (the upstream side with reference to a direction of transport ofthe liquid) communicates with a storage portion of the liquid in thecartridge 20. The tube 21 has a resiliency to an extent to close whenpressed by the fingers 22 and restore when a force from the fingers 22is released. The tube 21 is arranged in a partially arcuate shape alongan inner surface of a tube guide wall 25 of the cartridge 20. Thearcuate portion of the tube 21 is arranged between the inner surface ofthe tube guide wall 25 and the plurality of fingers 22. A center of thearc of the tube 21 matches a center of rotation of the cam 11.

The fingers 22 are members for closing the tube 21. The fingers 22operate upon reception of a force from the cam 11. The fingers 22 eachinclude a rod-shaped shaft portion and a flange-shaped pressing portionand is formed into a T-shape. The rod-shaped shaft portion comes intocontact with the cam 11, and the flange-shaped pressing portion comesinto contact with the tube 21. The fingers 22 are supported so as to bemovable along an axial direction.

The plurality of fingers 22 are arranged radially from the center ofrotation of the cam 11 at regular distance. The plurality of fingers 22are arranged between the cam 11 and the tube 21. Here seven fingers 22are provided. In the following description, fingers may be referred toas a first finger 22A, a second finger 22B, . . . , and a seventh finger22G from the upstream side of the direction of transport of the liquid.

The cam 11 has projecting portions 11A at four positions on an outerperiphery thereof. The plurality of fingers 22 are arranged on the outerperiphery of the cam 11, and the tube 21 is arranged on the outside ofthe fingers 22. The fingers 22 are pressed by the projecting portions11A of the cam 11, so that the tube 21 is closed. When the fingers 22come out of contact with the projecting portions 11A, the tube 21 isrestored to the original shape by resiliency of the tube 21. When thecam 11 rotates, the seven fingers 22 are pressed in sequence by theprojecting portions 11A, and close the tube 21 in sequence from theupstream side in the direction of transport. Accordingly, when the tube21 is caused to perform a peristaltic action, and liquid is compressedand transported to the tube 21.

Drive Mechanism

The drive mechanism 12 is a mechanism configured to drive the cam 11 torotate and, as illustrated in FIG. 4, includes a piezoelectric actuator121, a rotor 122, and a deceleration transmitting mechanism 123.

The piezoelectric actuator 121 is an actuator for rotating the rotor 122by using vibrations of a piezoelectric element. The piezoelectricactuator 121 vibrates a vibrator by applying a drive signal on thepiezoelectric elements adhered to both surfaces of the rectangularvibrator. An end portion of the vibrator comes into contact with therotor 122, and when the vibrator vibrates, the end portion vibrateswhile tracing out a predetermined orbit such as an oval orbit or afigure eight orbit. By the end portion of the vibrator coming intocontact with the rotor 122 at a portion of the vibration orbit, therotor 122 is driven to rotate. The piezoelectric actuator 121 is biasedtoward the rotor 122 by a pair of springs so that the end portion of thevibrator comes into contact with the rotor 122.

The rotor 122 is a driven member rotated by the piezoelectric actuator121. The rotor 122 is provided with a rotor pinion which constitutespart of the deceleration transmitting mechanism 123.

The deceleration transmitting mechanism 123 is a mechanism configured totransmit a rotation of the rotor 122 to the cam 11 at a predeterminedgear ratio. The deceleration transmitting mechanism 123 includes therotor pinion, a transmitting wheel 123A, and a cam gear (see FIG. 11).The rotor pinion is a small gear integrally mounted on the rotor 122.The transmitting wheel 123A includes a large gear that engages the rotorpinion and a pinion that engages the cam gear, and has a function totransmit a rotational force of the rotor 122 to the cam 11. The cam gearis integrally mounted on the cam 11, and is rotatably supported togetherwith the cam 11. The gear ratio of the deceleration transmittingmechanism 123 is set to 40 here. In other words, when the rotor 122rotates by one turn, the cam 11 rotates by 1/40 turn.

The pump unit 5 includes the tube 21, the plurality of fingers 22, thecam 11 and the drive mechanism 12, and the cam 11 and the drivemechanism 12 are provided on the main body 10, and the tube 21 and theplurality of fingers 22 are provided on the cartridge 20. The main body10 is provided with a measuring unit 40 configured to measure therotational angle of the cam 11 or the like, a control unit 50 configuredto control the piezoelectric actuator 121 or the like, and a battery 19configured to supply power to the piezoelectric actuator 121 or thelike.

FIG. 6 is a block diagram for explaining the measuring unit 40 and thecontrol unit 50 of the liquid transport apparatus 1. While referring toFIG. 11 as well, the measuring unit 40 and the control unit 50 will bedescribed.

The measuring unit 40 includes a cam side measuring unit 41 formeasuring the rotational angle of the cam 11, and first and secondmeasuring units 42 and 43 configured to measure first and secondrotational angles of the rotor 122.

The cam side measuring unit 41 is a rotary-type encoder including alight-emitting portion 41A and a light-receiving portion 41B. The camgear is provided with a cam-side reflecting portion 111 formed thereon,and the cam-side reflecting portion 111 reflects light from thelight-emitting portion 41A and the light-receiving portion 41B receivesthe reflected light. The light-receiving portion 41B outputs an outputsignal CAM_Z in accordance with an amount of received light to thecontrol unit 50.

The first and second measuring units 42 and 43 are also rotary-typeencoders provided with light-emitting portions 42A and 43A andlight-receiving portions 42B and 43B. The rotor 122 is provided withfirst and second reflecting portions 124 and 125 formed thereon. Thefirst reflecting portions 124 reflect light from the light-emittingportion 42A of the first measuring unit 42 and the light-receivingportion 42B of the first measuring unit 42 receives the reflected light.The second reflecting portion 125 reflects light from the light-emittingportion 43A of the second measuring unit 43, and the light-receivingportion 43B of the second measuring unit 43 receives the reflectedlight. The light-receiving portions 42B and 43B of the first and secondmeasuring units 42 and 43 output output signals ROT_A and ROT_Z inaccordance with the amount of received light to the control unit 50,respectively.

FIG. 7 is an explanatory drawing of the cam-side reflecting portion 111formed on the cam gear. As illustrated in FIG. 7, one cam-sidereflecting portion 111 is formed on the cam gear. A positionalrelationship of the cam-side reflecting portion 111 with respect to theprojecting portions 11A differs from one product to another.

FIG. 8 is an explanatory drawing of the first and second reflectingportions 124 and 125 formed on the rotor 122. As illustrated in FIG. 8,the numbers of the first and second reflecting portions 124 and 125 aretwelve and one, respectively. The twelve first reflecting portions 124are formed radially about a rotating shaft of the rotor 122equidistantly at regular intervals. Therefore, an angle between thefirst reflecting portions 124 is 30 degrees. The second reflectingportion 125 is formed solely on an inner side of the first reflectingportions 124, that is, on the rotating shaft side of the rotor 122.

The cam side measuring unit 41 and the first and second measuring units42 and 43 are not limited to a reflective optical sensor, but may be atransmissive optical sensor.

The control unit 50 includes a counter 51, a memory unit 52, anoperating unit 53, and a driver 54. The counter 51 counts the number ofedges included in the output signal ROT_A from the first measuring unit42. The counted value of the counter 51 indicates the rotational angleof the rotor 122. Since the rotational angle of the rotor 122 and therotational angle of the cam 11 correspond to each other, the countedvalue of the counter 51 indicates also the rotational angle of the cam11. The memory unit 52 memorizes a program used by the operating unit 53for driving the driver 54, and memorizes a position on the output signalROT_A corresponding to the pump original point. The operating unit 53executes the program memorized in the memory unit 52, and drives thedriver 54 on the basis of the counted value of the counter 51 (therotational angles of the cam 11 and the rotor 122) and the position onthe signal ROT_A corresponding to the pump original point. The driver 54outputs a drive signal to the piezoelectric actuator 121 of the drivemechanism 12 in accordance with an instruction from the operating unit53.

As described later, the control unit 50 corresponds to a determiningunit configured to determine a reference of the output signal ROT_A onthe basis of the signal ROT_Z output after an output of the signalCAM_Z. The control unit 50 corresponds to a reference point searchingunit configured to obtain a reference point of the signal ROT_A.

Actions of Liquid Transport Apparatus

FIG. 9 is a graph showing a relationship between an amount of rotationof the cam 11 and an accumulated amount of transportation. This graphindicates a result of measurement of an accumulation of the amount oftransportation with respect to the amount of rotation of the cam 11 froma reference position, which is a location of the cam 11 and is assumedto 0 degree.

Here, while the cam 11 rotates from 0 degree to 60 degrees (hereinafter,referred to as “transportation period”), the amount of transportation issubstantially proportional to the rotational angle. In thistransportation period, the liquid is transported by closing the tube 21from the first finger 22A in sequence. While the cam 11 rotates from 60degree to 80 degrees (hereinafter, referred to as “steady period”), theaccumulated amount of transportation does not change. In this steadyperiod, the seventh finger 22G continuously closes the tube 21. Whilethe cam 11 rotates from 80 degree to 85 degrees (hereinafter, referredto as “reverse flow period”), the accumulated amount of transportationdecreases. In other words, liquid flows reversely in the reverse flowperiod.

FIG. 10A and FIG. 10B are explanatory drawings relating to a reverseflow of liquid. The tube 21 is arranged in an arcuate shape as describedabove. Here, however, for the sake of convenience of description, thetube 21 is illustrated as being straight.

By the rotation of the cam 11 as illustrated in FIG. 10A, a state istransferred from a state in which the seventh finger 22G closes the tube21 to a state in which the pressed state by the seventh finger 22G isreleased as illustrated in FIG. 10B. At this time, liquid flowsreversely by a difference in volume obtained by subtracting a volumeindicated by a hatched portion in FIG. 10A from a volume indicated by ahatched portion in FIG. 10B.

While the cam 11 rotates from 85 degree to 90 degrees (hereinafter,referred to as “restoration period”), liquid of an amount correspondingto a reverse flow is transported. In other words, the reference positionand 0 degree correspond to the position of the cam 11 after therestoration period.

In this manner, when the cam 11 is rotated, there are a period in whichliquid of an amount corresponding to the amount of rotation istransported, a period in which the liquid is not transported, and aperiod in which the liquid flows reversely. As a result, as illustratedin FIG. 9, the amount of transportation of the liquid with respect tothe amount of rotation of the cam 11 differs depending on the rotationalangle of the cam 11. For example, in the case where the liquid istransported by rotating the cam 11 by 45 degrees, the amount oftransportation when the cam 11 is rotated from 0 degree to degrees(approximately 1.2 μl) and the amount of transportation when the cam 11is rotated from 45 degrees to 90 degrees (approximately 0.3 μl) aredifferent. In contrast, in the case where the liquid is transported byrotating the cam 11 by 90 degrees, the liquid of the substantially sameamount (approximately 1.5 μl) is transported irrespective of theposition of the cam 11. In other words, the amount of transportation ofthe liquid is non-linear with respect to the rotation of the cam 11, buthas periodicity with a cycle of ¼ turn of the cam 11.

Setting Procedure of Signal Original Point

From the viewpoint of transportation of liquid with high degree ofaccuracy, the accumulated amount of transportation of the liquid ispreferably linear with respect to time. In order to do so, for example,the cam 11 needs to be adjusted to rotate faster in the reverse flowperiod and the restoration period than in the steady period. In order todo so, the counted value of the counter 51, that is, the rotationalangle of the cam 11 and the amount of transportation of the liquid needto be coordinated accurately.

FIG. 11 is an enlarged drawing of the cam 11, the rotor 122, thetransmitting wheel 123A, the cam side measuring unit 41, and the firstand second measuring units 42 and 43 in FIG. 4. FIG. 12 is anexplanatory drawing illustrating a relationship between the signalsCAM_Z, ROT_Z and ROT_A. FIG. 13 is an explanatory drawing illustrating arelationship between the signals CAM_Z and ROT_A. The signals CAM_Z andROT_A in FIG. 13 are illustrated with a time axis enlarged more thanthat in FIG. 12.

As described above, the first measuring unit 42 outputs the signal ROT_Ain accordance with the amount of the reflected light received by thelight-receiving portion 42B. Here, as illustrated in FIG. 11, the rotor122 is provided with twelve first reflecting portions 124 in thecircumferential direction. Therefore, the first measuring unit 42outputs the signal ROT_A including twelve pulsed waveforms every timewhen the rotor 122 rotates by one turn.

The second measuring unit 43 outputs the signal ROT_Z in accordance withthe amount of the reflected light received by the light-receivingportion 43B. Here, the rotor 122 is provided with one second reflectingportion 125. Therefore, the second measuring unit 43 outputs the signalROT_Z including one pulsed waveform every time when the rotor 122rotates by one turn.

As described above, the cam-side measuring unit 41 outputs the signalCAM_Z in accordance with the amount of the reflected light received bythe light-receiving portion 41B. The cam 11 is provided with onecam-side reflecting portion 111 formed thereon and the cam-sidemeasuring unit 41 outputs the signal CAM_Z including one pulsed waveformevery time when the cam 11 rotates by one turn.

Here, since the rotor 122 rotates by 40 turns while the cam 11 rotatesby one turn, the number of pulses included in the output signal ROT_A ofthe first measuring unit 42 corresponding to the rotor 122 in one cycleof the output signal CAM_Z of the cam side measuring unit 41 is40×12=480. If a leading edge and a fall edge of pulses of the signalROT_A are determined to be one count respectively, 960 counts from 0 to959 are measured every time when the cam 11 rotates by one turn asillustrated in FIG. 12.

In order to coordinate the signal ROT_A to the cycle of the signal CAM_Zaccurately for measuring the rotational angle of the cam 11 accurately,the edge included in the signal CAM_Z is ideally steep, for example, asillustrated in FIG. 12. Actually, however, the edge of the signal CAM_Zis dull as illustrated in FIG. 13. It is because the rotation of the cam11 is slower than the rotation of the rotor 122, a change of the signalCAM_Z is gentler than the signal ROT_A. Consequently, timing when theedge included in the signal CAM_Z is detected is slightly deviateddepending on the cycle as illustrated by a solid line and a broken linein FIG. 14. Therefore, when an attempt is made to determine the signaloriginal point of the signal ROT_A directly from the signal CAM_Z,reproducibility of the signal original point of the signal ROT_A is low.Therefore, in the embodiment, the signal original points from the signalCAM_Z to the signal ROT_A are determined in the following manner.

FIG. 14 is a flowchart illustrating a procedure for specifying thesignal original point of the signal ROT_A. With reference to FIG. 12 aswell, specification of the signal original point of the embodiment willbe described.

First of all, in Step S11, the control unit 50 detects a leading edge ofthe pulsed waveform of the signal CAM_Z. Subsequently, in Step S12, thecontrol unit 50 detects an edge of the signal ROT_Z appearingimmediately after the detection of the edge of the signal CAM_Z asindicated by an arrow from the signal CAM_Z to the signal ROT_Z in FIG.12. As described above, the signal ROT_Z is a signal having a cycle ofone turn of the rotor 122, timing when the edge of the signal CAM_Z isdetected is constant with respect to the signal ROT_Z. Therefore, theedge of the signal ROT_Z is detected with high reproducibility by theprocess described above. Subsequently, in Step S13, the control unit 50detects an edge of the signal ROT_A appearing immediately after thedetection of the edge of the signal ROT_Z as indicated by an arrow fromthe signal ROT_Z to the signal ROT_A in FIG. 12, and determines thisedge as the signal original point. As described above, since the signalROT_A and the signal ROT_Z are derived from a light amount of reflectedlight from the first and second reflecting portions 124 and 125, thefirst and second reflecting portions 124 and 125 are formed on the rotor122, and the signal ROT_A corresponds accurately with the cycle of thesignal ROT_Z. Therefore, the signal original point of the signal ROT_Ais determined with high reproducibility by the process described above.

Pump Original Point Determination Process

FIG. 15 is a schematic diagram for explaining pump original pointdetermination. FIG. 16 is a flowchart illustrating a procedure for thepump original point determination process. With reference also to FIG.9, the pump original point determination process will be described.

After the determination of the signal original point, a process ofdetermining the pump original point is performed. It is because thesignal original point does not match the pump original point which is tobe determined from the view point of control in constant amount liquidfeeding since the signal original point is determined fromreproducibility point of view.

Pump Original Point

Here, the position where the reversely flowed liquid returns by anamount corresponding to the reverse flow, that is, the referenceposition of the cam 11 in FIG. 9 may be employed as the pump originalpoint. By setting the pump original point in this manner, one boundaryis enough between the transportation period and an intermittent period(including the steady period, the reverse flow period, and therestoration period) in one cycle in the amount of transportation ofliquid, and hence the number of variables required for control, forexample, may be reduced, so that control of the constant transportationis facilitated.

The rotational angle of the cam 11 corresponding to the pump originalpoint may be obtained easily by image processing. Here, for the sake ofconvenience of description, a solid line with an arrow extending from arotating shaft of the cam 11 in the radial direction is determined asthe pump original point as illustrated in FIG. 15.

Procedure of Pump Original Point Determination Process

The cam 11 is aligned with the rotational angle corresponding to thesignal original point, and the pump original point determination processis started.

In Step S21, the cam 11 is rotated by an angle corresponding to onecount of the signal ROT_A. In other words, the cam 11 is rotated by acam rotating unit provided on a manufacture line, for example, so that avalue Z counted from the signal original point increments by one in thesignal ROT_A. The value Z increments by one every time when Step S21 isexecuted.

Subsequently, an image of the cam 11 is captured in Step S22. Capturingof the image is performed by using a camera (image-pickup unit) providedin the manufacture line, for example.

In Step S23, the rotational angle of the cam 11 is detected by analyzingthe captured image. Specifically, in the first embodiment, the positionsof the projecting portions 11A are detected by detecting edges of theprojecting portions 11A of the cam 11 from the captured image. Here, thereason why the edges of the projecting portions 11A of the cam 11 aredetected is because displacement of the projecting portions 11A of thecam 11 is significantly larger than the rotation by an anglecorresponding to one count of the signal ROT_A because the projectingportions 11A are apart from the rotating shaft of the cam 11, so that aminute change in rotational angle of the cam 11 appears in a change ofthe projecting portions 11A of the cam 11. In other words, accuracy ofedge detection may be improved.

Subsequently, in Step S24, whether or not the rotational angle of thecam 11 reaches the pump original point is determined. If the cam 11 isdetermined to have reached the pump original point, the procedure goesto the next Step S25, and if the rotational angle of the cam 11 isdetermined not to have reached the pump original point, the proceduregoes back to Step S21. In Step S25, the counted value Z is memorized inthe memory unit 52 of the control unit 50, and a series of process isterminated.

In this manner, the position on the signal ROT_A corresponding to thepump original point is determined to an edge behind the signal originalpoint by the value Z.

After the pump original point determination process, the control unit 50performs the transportation of the liquid as described below. First ofall, the control unit 50 drives the piezoelectric actuator 121, rotatesthe rotor 122 and the cam 11, and detects the edge of the signal CAM_Z.On the basis of the edge of the signal ROT_Z detected immediately afterthe edge of the signal CAM_Z is detected, the control unit 50 detects anedge of the signal ROT_A (signal original point) detected immediatelythereafter. The control unit 50 counts the edges of the signal ROT_Aafter the detection of the signal original point, and further rotatesthe rotor 122 and the cam 11 until the counted number of edges reachesthe number of edges Z memorized in the memory unit 52. When the countednumber of edges reaches the value Z, the cam 11 is located at arotational angle corresponding to the pump original point. Accordingly,as illustrated in FIG. 9, the control unit 50 rotates the cam 11 at aconstant rotational angle during the transportation period from the pumporiginal point (the reference position corresponding to 0 degree in FIG.9) to 60 degrees, and rotates to 90 degrees so as to skip theintermittent period upon reaching 60 degrees. Accordingly, theaccumulated amount of transportation of liquid can be increased linearlywith respect to time. In other words, transportation of liquid with highdegree of accuracy is realized.

As described above, in the first embodiment, on the basis of the edge ofthe signal ROT_Z detected immediately after the edge of the signal CAM_Zis detected, the edge of the signal ROT_A detected immediatelythereafter is determined as the signal original point (reference point)of the signal ROT_A. Then, the cam 11 is rotated by an amountcorresponding to one count from the signal original point of the signalROT_A, and then is stopped, and the image of the cam 11 is captured.From the positions of the projecting portions 11A of the cam 11 obtainedby analyzing the image captured as described above, the fact that thecam 11 reaches the pump original point is determined. Subsequently, thecounted value Z from the signal original point of the signal ROT_A untilthe cam 11 reaches the pump original point is memorized in the memoryunit 52. Therefore, since the position to which the cam 11 is rotatedfrom the signal original point of the signal ROT_A by the counted valueZ is determined as the pump original point, the relationship between thesignal original point and the pump original point can be obtainedeasily.

Second Embodiment

FIG. 17 is a schematic drawing illustrating an example of the pump unit5 of a second embodiment.

In the second embodiment, a method of detecting the rotational angle ofthe cam 11 in Step S23 of the pump original point determination processis changed. In other words, the projecting portions 11A of the cam 11each are provided with a position detection mark M1 such as a thin lineor cross lines as illustrated in FIG. 17. The image of the cam 11captured in Step S22 is analyzed to detect positions of the marks M1,and the rotational angle of the cam is detected on the basis of theresult of detection. The reason why the position detection marks M1 aremarked on the projecting portions 11A of the cam 11 is that adisplacement of the marks M1 with respect to the rotation by an anglecorresponding to one count of the signal ROT_A is sufficiently largebecause the marks M1 are apart from the rotating shaft of the cam 11,and hence the edge detection with high degree of accuracy is achieved.

As described above, in the second embodiment, the position detectionmarks M1 are marked on the projecting portions 11A of the cam 11, andthe fact that the cam 11 reaches the pump original point is determinedfrom the positional relationship of the marks M1 obtained by analyzingthe captured image of the cam 11. Since the position to which the cam 11is rotated from the signal original point of the signal ROT_A by thecounted value Z is determined as the pump original point, therelationship between the signal original point and the pump originalpoint can be obtained easily.

Third Embodiment

FIG. 18 is a schematic drawing illustrating an example of the pump unit5 of a third embodiment. The third embodiment will be described withreference also to FIG. 9 and FIG. 10.

In the third embodiment as well, a method of detecting the rotationalangle of the cam 11 in Step S23 of the pump original point determinationprocess is changed. In other words, positions of the fingers 22 aredetected by image analysis, and the rotational angle of the cam 11 maybe determined on the basis of the result of detection. As a method ofdetecting the positions of the fingers 22, for example, the edges of thefingers 22 are detected by using the image captured in Step S22 forexample, and the rotational angle of the cam 11 may be determined fromthe detected positions of the fingers 22. For example, in a manner thatthe cam 11 reaches the reference position in FIG. 9 when the fingers 22Ato 22G are at the positional relationship as illustrated in FIG. 10B,the positional relationship of the fingers 22 is coordinated with therotational angle of the cam 11, and hence the fact that the cam 11reaches the reference position may be known by detecting the fact thatthe fingers 22 are at the predetermined positions.

Alternatively, position detection marks M2 may be marked on the fingers22 in advance as illustrated in FIG. 18 to determine the rotationalangle of the cam 11 from a change of the position detection marks M2 inthe captured image. In FIG. 18, although the marks M2 are marked on allof the fingers 22, the mark M2 may be marked on some of the fingers 22as long as the rotational angle of the cam 11 can be specified.

As described above, in the third embodiment, the fact that the cam 11reaches the pump original point is determined from the positionalrelationship of the fingers 22 obtained by analyzing the captured imageof the cam 11. Since the position to which the cam 11 is rotated fromthe signal original point of the signal ROT_A by the counted value Z isdetermined as the pump original point, the relationship between thesignal original point and the pump original point can be obtainedeasily.

Others

The embodiments described above are for facilitating the understandingof the invention, and are not for interpreting the invention in alimited range. It is needless to say that the invention may be modifiedor improved without departing the scope of the invention and equivalentsare included in the invention. For example, the pump original point maybe obtained by combining the first embodiment and the third embodiment.

The entire disclosure of Japanese Patent Application No. 2014-16650,filed Jan. 31, 2014 is expressly incorporated by reference herein.

What is claimed is:
 1. A liquid transport method for a liquid transportapparatus comprising: rotating a cam from a reference position ofrotation of the cam rotating for transporting liquid; determiningwhether or not the cam rotates to a predetermined rotational angle onthe basis of an image of the liquid transport apparatus captured whenthe cam is rotated and stopped; and memorizing a signal value indicatinga rotational angle of the cam from the reference position of rotationuntil the cam rotates to the predetermined rotational angle.
 2. Theliquid transport method according to claim 1, further comprisingdetecting a position detection mark provided on the cam from the imageto detect the rotational angle of the cam.
 3. The liquid transportmethod according to claim 2, further comprising detecting an edge of theposition detection mark to detect the rotational angle of the cam. 4.The liquid transport method according to claim 1, further comprisingdetecting a position of a pressing member configured to press a memberwhich defines a flow channel of the liquid in association with arotation of the cam from the image to detect the rotational angle of thecam.
 5. The liquid transport method according to claim 1, wherein therotational angle of the cam when the reversely flowed liquid returns byan amount corresponding to the reverse flow is used as a reference ofthe predetermined angle.
 6. A liquid transport method for a liquidtransport apparatus comprising: rotating a cam configured to rotate fortransporting liquid; reading a memorized signal value indicating arotational angle of the cam rotating from a reference position ofrotation to a predetermined rotational angle, determining whether or notthe cam rotates from the reference position to the predeterminedrotational angle, and rotating the cam to a desired rotational anglewith reference to a position where the cam is determined to have rotatedto the predetermined rotational angle.
 7. The liquid transport methodaccording to claim 6, wherein with reference to the position where thecam is determined to have rotated to the predetermined rotational angle,the cam is rotated at a predetermined speed until the cam reaches afirst rotational angle, and is rotated at a speed higher than thepredetermined speed from the first rotational angle to a secondrotational angle.
 8. The liquid transport method according to claim 6,wherein the memorized signal value indicating the rotational angle ofthe cam from the reference position of rotation until the cam rotates tothe predetermined rotational angle is a signal value indicating therotational angle of the cam from the reference position until the camrotates to the predetermined rotational angle which is obtained byrotating the cam from the reference position, and determining whether ornot the cam rotates to the predetermined rotational angle on the basisof an image of the liquid transport apparatus captured when the cam isrotated and stopped.
 9. A liquid transport apparatus comprising: a camconfigured to rotate for transporting liquid, and a control unitconfigured to read a memorized signal value indicating a rotationalangle of the cam rotating from a reference position of rotation to apredetermined rotational angle, determine whether or not the cam rotatesfrom the reference position to the predetermined rotational angle, androtate the cam to a desired rotational angle with reference to aposition where the cam is determined to have rotated to thepredetermined rotational angle.